This invention relates to a package-type compressor of the type used for air compression, refrigeration and air-conditioning, etc., and more particularly to a package-type compressor using an oil-free scroll compressor element. An oil-free scroll compressor, which does not use oil such as a lubricating oil for the flow passage of the operation gas, is a well known compressor for use in air compression, refrigeration, and air-conditioning.
In this oil-free scroll compressor, two sealed spaces are defined by laps and end plates on the outer wall surface of an orbiting scroll lap and a stationary scroll lap by combining the orbiting scroll and the stationary scroll, each of which is equipped with spiral laps perpendicular to an end plate, while the inside of the laps face one another.
The sealed spaces move towards the center portion due to the relative motion of both scrolls. As their volumes thus decrease, a gas sucked from the outer peripheral sides of these scrolls is compressed and is discharged from a discharge port disposed at the center portion of the stationary scroll. When the operation gas is compressed in this way by the relative motion of the orbiting scroll and the stationary scroll, the scroll compressor generates heat. A discharge temperature of the operation gas reaches to about 190 to about 240.degree. C.
To increase a capacity of compressor, the scroll compressor element which is so-called a double scroll compressor, is proposed recently. The double scroll compressor has scroll laps on both sides of the end plate of the orbiting scroll.
It is impossible to use one side of the end plate of the orbiting scroll for cooling in case of the double scroll, as the conventional scroll compressor is possible. Therefore, cooling holes are formed through the end plate of the orbiting scroll of the double scroll.
An example of such a system is described in Japanese Patent Laid-open No. 8-219067/1996 and Japanese Patent Laid-open No. 8-261180/1996.
Though it is considered how to cool the compressor element itself in these publication, it does not take into consideration of cooling the whole compressor when it is packaged. That is, the double scroll compressor element applied to the package-type compressor generates vast heat compared with a conventional scroll compressor elements at the center of the orbiting scroll.
It is, therefore, needed to use a cooling air sucked from outside of a casing of the package-type compressor effectively. To cool the compressor effectively, a flow rate of a blow gas to the compressor has been increased until now. According to this technique, however, the cooling effect has not improved by increasing the blow gas on the double scroll compressor, because an area for cooling is restricted owing to a presence of scroll laps on both side of the orbiting scroll.
A noise caused by a cooling gas flow increases, when the blow gas flow rate has increased to get more effective cooling. Further, a bad influence has increased on a circumstance around the casing of the compressor by a hot air discharged from the package-type compressor after cooling. Therefore, it costs much for soundproofing and discharging exhaust gas after cooling to a place far away.